1. Technical Field
The present invention relates to a vibrating piece substrate and a tuning-fork vibrating piece, and in particular, to a vibrating piece substrate and a tuning-fork vibrating piece in which a pad for the measurement of characteristics is provided.
2. Related Art
In the related art, various vibrating pieces are used in an electronic apparatus as a clock signal source. Of the vibrating pieces, in many cases, a tuning-fork vibrating piece is used which is easy to manufacture and excellent in frequency-temperature characteristics. A method of manufacturing a tuning-fork vibrating piece is known in which a substrate (wafer) formed of a piezoelectric material, such as quartz, is etched in the form of the base portions of a plurality of tuning-fork vibrating pieces being connected to a frame, and the base portions of the respective tuning-fork vibrating pieces are folded and cut off from the frame (for example, see JP-A-2008-178021).
However, there are many cases where a cut mark is generated in a portion where the tuning-fork vibrating piece is folded and cut off. When a tuning-fork vibrating piece with a cut mark is accommodated in a package, the folded and cut portion comes into contact with the package, and intensive vibration or impact is applied from the outside. For this reason, quartz cracking may occur from the cut mark and a support arm or the like may be damaged. In order to solve such problems, a folding and cutting portion is provided in the support arm, not in the base portion (for example, see JP-A-2008-177723 and JP-A-60-070811).
In the related art, the characteristics, such as a frequency and a CI (Crystal Impedance) value, were measured before the respective tuning-fork vibrating pieces were folded and cut off. Measurement pads with which a measurement probe comes into contact may be arranged in the base portion if the area of the base portion is comparatively large (for example, see JP-A-2009-150678). In recent years, with the reduction in size of the tuning-fork vibrating piece, the area of the base portion decreases, such that the measurement pads may not be arranged in the base portion. In measuring the characteristics of the tuning-fork vibrating piece, the measurement probe is in direct contact with the measurement pads. In this case, it is necessary that the measurement pads have an area in a range of about 0.02 to 0.04 mm2 so as to maintain the strength of the measurement pads, and it is impossible to further reduce the area of each of the measurement pads. For this reason, in recent years, the measurement pads are provided in a frame portion close to the base portion (for example, see JP-A-2008-178021).
However, if the measurement pads are provided in the frame portion near the base portion, the measurement pads occupy a space, causing a decrease in the number of tuning-fork vibrating pieces per vibrating piece substrate.